ABSTRACT
ABSTRACT: The study of complex materials (non homogeneous matrices containing medium and/or heavy atoms as major elements) by PIXE requires the tailoring of the experimental set up to take into account the high x-ray intensity produced by these main elements present at the surface, as well as the expected low intensity from other elements “buried” in the substrate. Additionally, high Z matrices have a high x-ray absorption capability and are not always homogeneous. The non-homogeneity may be, on the one hand, a layered structure (which is uneasy to profile by Rutherford Backscattering Spectroscopy (RBS) if the material contains elements of neighbouring masses or if the layered structure extends on several microns). PIXE measurements at various incident energies (and with various projectiles (p, d, He3, He4)) are then an alternative method to overcome those difficulties. The use of special filters to selectively decrease the intensity of the most intense x-ray lines, the accurate calculation of the characteristic x-ray intensity ratios (Kα/Kβ, Lα/Lβ) of individual elements, the computation of the secondary x-ray fluorescence are amongst the most important parameters to be investigated in order to solve these difficult analytical problems. Examples of Cu, Ag and Au based alloys with various coatings as encountered in Amerindian metallurgy are discussed. Special application to Pre-Hispanic gold jewellery has been developed. Amerindian goldsmiths have indeed used original techniques to manufacture and to gild ornaments and artefacts. Goldmetallurgy in ancientAmerica wasmainly a surface technology. Surface studies of artefacts fromvarious regions of Pre-Hispanic SouthAmericawere carried out using protonmilliandmicrobeams (from1mmdown to 10µmdiameter). Outstanding aspects about themetallurgical processes involved in the gilding of the artefacts have been established.
